Response characteristics of Very Low Frequency transmitter signals in Antarctica to geomagnetic storm events

As the peak of the 25th solar cycle approaches, strong geomagnetic storm events are becoming more frequent, often accompanied by intense radiation belt particle precipitation. These changes significantly impact ionospheric electron density, affecting radio wave propagation and the quality of communication and navigation. Based on 18 moderate or stronger geomagnetic storm events that occurred between 2022 and 2023, this study analyzes the variation characteristics and patterns of Very Low Frequency (VLF) signals during these storms using data received at the Great Wall Station (GWS) in Antarctica from 4 VLF transmission stations: NAA, NML, NLK, and NPM. The results show that signal disturbances caused by geomagnetic storms mainly occur during sunset and nighttime, with the VLF signal response significantly delayed relative to the Dst index. The average time interval between the maximum signal amplitude change and the minimum Dst value is approximately 5.04 h. The correlation between signal amplitude changes and storm intensity is weak, with the average amplitude change of the nighttime paths being 5.30 dB, 3.23 dB for daytime paths, and 6.04 dB during sunset. The average disturbance duration is 1.55 h and shows little correlation with storm intensity. The VLF signal disturbances caused by geomagnetic storms are closely related to the drift-loss process of radiation belt high-energy particles. The degree of signal variation is influenced by the initial electron density of the ionospheric D layer. The results provide valuable insights into the VLF signal variation characteristics during geomagnetic storms and their relationship with radiation belt particle precipitation, offering a crucial reference for future ionospheric disturbance monitoring and the evaluation of communication system impacts based on VLF signals.